Circuit interrupter



Jan. 12, 1954 v L. R. LUDWIG ET AL CIRCUIT INTERRUPTER 2 Sheets-Sheet 1Filed June 29, 1950 Fig.9.

Fig.8.

INVENTORS Leon R. Ludwiq,Wlmhrop M. Leeds ,Banjumin P. Baker 8 JamesM.Cumminq,deceused,by Helen J. 0ummlnq,ExecuIrh 66a 4 1 i7 ATTO EYWITNESSES:

Z. 4? 63ml- 2 Sheets-Sheet 2 Filed June 29, 1950 Fig.5.

Fig.2.

a 1m Y B 2 f w a a 9 7 8 m w m FN 6 w INVENTORS Leon R. Ludwig,WinthropM. Leeds, Benjamin F. Baker 8. James M.Gumminq,dcceased,byHelemLOummlnq,Executrix.

V/vVV/V//////////%///////////////Q \\\\\\\\\2 5W9 i l 2 8 H 3 I 2 mmlPatented Jan. 12, 1954 UNITED STATES Far ENT OFFICE CIRCUIT lNTERRUPTERApplication June 29, 1950, Serial No. 171,158

This invention relates to circuit interrupters in general, and, moreparticularly, to arc-extinguishing structures for circuit interruptersof the liquid-break type.

A general object of our invention is to provide an improved liquid-breaktype of circuit interrupter which will more effectively interrupt thecircuit therethrough than has heretofore been attained.

Another object is to provide an improved liquid-break circuitinterrupter in which an improved piston construction is employed to moreeffectively drive liquid through the arc to extinguish the same.

A more specific object is to provide an improved circuit interrupter ofthe type specified in the immediately preceding paragraph in which thearc is drawn along the central vertical axis of the interrupter, and inwhich the design is symmetrical with no unbalanced horizontal mechanicalforces.

Still another object is to provide an improved piston construction for aliquid-break type of circuit interrupter in which improved time-delaymeans are providedbefore application of the liquid to the arc.

Another object is to provide an improved differential pistonconstruction of the liquid break t p Further objects and advantages willreadily become apparent upon reading the following specification takenin conjunction with the drawings, in which:

Figure l is a side elevational view, partially in vertical section, of atank-type liquid-break circuit interrupter employing our invention andshown in the closed-circuit position; Fig. 2 is an enlarged verticalsectional view through the left-hand arc-extinguishing unit of Fig. 1,the contact structure being shown in the closed-circuit position;

Fig. 3 is a view similar to that of Fig. 2, but showing the dispositionof the contact structure at an intermediate point in; the openingoperation during the interruption of high-amperage currents;

9 Claims. (Cl. 200150) Fig. 4 is a sectionalview taken along'the line atan intermediate 'point in the opening Opera tion during theinterruption-of high amperage currents;

Fig. 7 is a sectional view taken alOng the lin VIIVII'of Fig. 5;

Fig. 8 illustrates still another form of our in-'- vention, the contactstructure being shown in the closed-circuit position;

Fig. 9 is a view similar to that of Fig. 8 but indicating the partiallyopemcircuitposition of the contact structure, and e r Fig. 10 is asectional view taken along the line X--X of Fig. 8.

Referring to the drawings, and more particularly to Fig. 1 thereof, thereference character I designates a tank filled to the level 2 with asuitable arc-extinguishing liquid, in this instance circuit breaker oil.Depending from the cover 3 of the tank I are a pair of terminal bushingsi, 5, to the lower ends of which are secured identical arc-extinguishingunits, generally designat'ed by the reference numeral 6. Electricallyinterconnecting the units 6 in the closed circuit position, shown by thefull lines in Fig. 1, is a conducting cross-bar I actuated vertically byan insulating lift rod 8, and having at its opposed extremitiesrod-shaped movable contacts 9.

Referring to Figs. 2-4, which more clearly show the internalconstruction of the arc-extinguishing units 6, it will be apparent thatwe have provided an elongated insulating casing Ill having an internallydisposed insulating sleeve II, the latter having an enlarged portion I2and a restricted portion I3. An aperturedpartition plate I4 is disposedupon an internally provided flange I5 of the casing I 0. The aperture I6provided in the partition plate I4 accommodates longitudinal travel of amovable contact assembly, generally designated by the referencecharacter I1, and including an intermediate contact I8, a hollow pistonmember I9 and a driving piston 20.

It will be noted that in the closed circuit position, shown in Fig. 2,the movable contact 9 engages the intermediate contact I8, the latter inturn engaging a relatively stationary contact 2|, which is preferablyresiliently mounted by means of a stem 22 and a compression spring 23. Ashunt 24 electrically connects the stem 22 with the apertured coverplate 25 of the unit 6. The cover plate 25 may be suitably secured by aclamp 26 (Fig. 1) to the lower end of the terminal bushings 4, 5.

The hollow piston member I 9 consists of a plurality of aperturedinsulating plates 21, 28 having different internal diameters.Preferably, insulating tie rods 29 (Fig. 4) are provided to se- Valvemeans 33 are provided to permit oil to leave the chamber 34 in back ofthe piston 2|! during the closing operation. Such valve means preferablyincludes a valve sleeve .35 picked up by a flange 36 secured to andmovable with the movable contact 9. Apertures 31 are provided in thepiston 20 to permit the ,exit of oil out of the chamber 34 during theclosing stroke.

The opening operation of this form of our invention will now bedescribed. In the closed circuit position of the interrupter, shown inFigs. 1 and 2, the electrical circuit therethrough includes terminalbushing 4, conducting cap 25, flexible shunt 24, relatively stationarycontact 21, intermediate contact 18, lower movable contact 9 and throughthe conducting cross-bar 'l :to the right-hand unit 5. The circuitextends through the right-hand unit 6 in the same mannor previouslydescribed to the right-hand terminal bushin 5.

During the opening operation, suitable mechanism, not shown, eitherresponsive to manual operation or to the existence of overload conditionexisting in the electrical circuit controlled by the interrupter,operates to cause downward opening movement of the lift rod 3. Thedownward, motion of lift rod 8 carries with it the two movable contacts,19, iConsidering only the lefthand unit L6, ,it will be apparent thatthe com pression spring 32 forces the driving piston 20 and the entiremovable contact assembly ll downwardly, drawing an are 38 more clearlyShown in Fig. 3. Since the valve 33 is open, the assembly 11 movesdownwardly freely until the piston member 19 e ters the restrictedportion 13, at which time oil is ,forced through the inlet passages 39and against the are 38 and upward-v 1y through the interior 40 of thehollow piston member la. Since the movable contact assembly I! slows upafter the piston member l9 enters the restriction 13, the movablecontact s will separate from the intermediate C nt ct F8 to draw asecond serially related arc 4|, more clearly shown in Fig. .3,

During the interruption of heavy currents, the pressure generated by theare 4! within the piston chamber 34 will be high, closing the valve 33and assisting the compression spring 32 in driving the piston '20downwardly, as shown in Fig. 3. During the interruption of lightcurrents, where the pressure generated by the are 4:! is negligible,dependence must be had upon the compression spring 32 alone to bringabout the necessary downward opening motion of the movable contactassembly [1.

"The upward flow of oil indicated by the arrows in Fig. 13 through theinterior ,40 f the his- .ton member l9 causes extinction of the are 38and hence circuit interruption, In the ;fully open circuit position, thelower movable contact 9 is withdrawn out of the piston member '20 to anopen circuit disconnect position indicated by the dotted lines 42 ofFig. ,1.

During the closing operation, the lift rod 8, cross-bar 1 and movablecontacts 9 move upward- 13/. The contact 9 enters the valve means 33 ofthe piston 20 and causes enga ment between the flange 3.6 and the valvesleeve 35, thereby opening the valve means .33.

,The movable contact 9 strikes the intermediate contact [8 and moves theintermediate contact l8, and hence the assembly I1, upwardly untilengagement is made between relatively stationary contact 2| andintermediate contact I8, the compression spring 23 providing therequisite contact pressure. The circuit is then closed.

Figs. 5-7 illustrate another embodiment of our invention. In thisembodiment, the modified unit .44 has anintermediate contact 45connected by a lost-motion connection 46 with the movable contactassembly I]. In this form of our invention, :the piston member l9 movesalong vertical walls provided by an insulating sleeve 41 disposedinteriorly of the casing 10,

The operation is as follows. During the opening operation, the downwardopening movement of the contact 9 immediately permits fast downwardopening motion of the intermediate contact ,45 relative to the movablecontact assembly ll because of lost motion mechanical connection 4.6therebetween. The intermediate contact #5 is biased downwardly by acompression spring 4,0 to a stop '50 on the connecting sleeve 5i. :Sincethe intermediate contact 45 is comparatively li ht, the are 38 (Fig. 6)will be very rapidly formed. The intermediate contact 45 will so n cometo its stop 50 and thereafter will move with the assembly ll, Thus thefirst few inches of arc length 138 are very rapidly formed. The movablecontact assembly i 1 willbe driven downwardly by the driving piston 20under the in fluence of the compression spring ,32. The'downward motionof the contact assembly H forces Oil within the region 48 through theinlet passages 39 and upwardly into the interior 4!] of the hollowpiston member i9 against the arc 3,8 Because of the relatively slowdownward travel of the assembly 1], the lower movable contact 8 willseparate from the lower contact portion 52 of the intermediate contact45 to establish the arc 4| asshown inFig. 6.

As before, during high current interruption. the pressure generated bythe an M within the piston chamber 34 will be high, closing the valvemeans 33 and assistin the compression sprin 32 in driv n th drivingpiston 20 downwardly- This condition is shown in Fig. 6. During low curent interrup i n. on the other hand. th pressure formed at the arc 4|will be :unall, and the valve means .33 will remain open so that oil maybe drawn through the apertures 31 into the region :34.

The upward flow of oil through thefhollow piston member I9 quickly'extinguishes the are 38 and the circuit is interrupted. As before, themovable contact 9 is withdrawn to the disconnect piston shown by thedotted'lines 42 ofFig. '1.

Figs. 8-10 illustrate a third embodiment of our invention utilizing adifferential piston construction in the modified unit 53. In thisembodiment, the casing 10 has the sleeve 11 con" structed, as before,.With the enlarged portion t2 and the restricted portion 13. Thedifferential piston membe ene ally desi nated y the reference character54, includes a hollow piston member 1 9 and two piston surfaces 55 and,56. Since the ar a of t e p stonsurface 5,6 is larger than the area ofthe piston surface .55, the piston member 54 will move downwardly,thereby aforeins oil out of the region 58. through inlet passages 5 8and d wnwardly through the interior .40 of the hollow piston-member 1:9.The com.

pression spring. 32,.as before, assists downward motion of the drivingpiston 20.

'In this embodiment, we have only a single are 60 being drawn bycooperation of the contacts 21, 9. If the pressure generated by the areG is small, reliance is largely had upon the biasing action exerted bythe compression spring 32. If the current being interrupted is high, theare 60 will generate a high pressure which will act upon the twosurfaces 55, 56.. Because of their unequal areas, the pressure will havea net effect in forcing the differential piston assembly 54 downwardly,thereby causing oil to travel from the region 59 through the inletpassages 58, and through the interior 40 of the piston member H) to theregion 34 in back of the lower piston 26. This condition is shown inFig. 9. V

The foregoing description of three embodiments of our invention showshow we have providedan improved liquid break type of circuit interrupterutilizing novel piston constructions for bringing about effectivecircuit interruption. During the interruption of relatively lightcurrents, dependence is placed upon the compression spring 32 ineffecting downward opening motion of the contact assemblies I 1 or thedifferential piston assembly 54. During high current interruption, thepressure generated will assist the compression spring 32 in eitherforcing the driving piston 20 of Figs. 2 and 5 downwardly, or elseforcing the diiierential piston 54 downwardly, thereby assisting thecompression spring 32.

It will be noted that the oil flow through the interior 40 of the hollowpiston member 19 is effective in extinguishing the arc 38 or til. Theinterior 40 is corrugated to minimize breakdown longitudinally of thepiston 19 due to carbonization of the insulating surfaces.

Although we have shown and described spe cific structures, it is to beclearly understood that the same were merely for the purpose ofillustration, and that changes and modifications may readily be madetherein by those skilled in the art without departing from the spiritand scope of the appended claims. a

We claim as our invention:

1. A circuit interrupter of the liquid break type including a casing, arod-shaped relatively stationary contact disposed adjacent one end ofthe casing, a movable contact assembly movable within the casingincluding a hollow piston member through which liquid may flow, anintermediate contact and a driving piston, the intermediate contactbeing cooperable with the relatively stationary contact to establish anarc which is subjected to the liquid now passing through the hollowpiston, a movable contact movable adjacent the other end of the casingand cooperable with the intermediate contact to establish a secondserially related arc, the rodshaped relatively stationary contactprotruding at least part way through the hollow piston member to engagethe intermediate contact in the closed circuit position of theinterrupter, liquid inlet passage means disposed in the movable contactassembly adjacent the point of engagement of the stationary andintermediate contacts, means biasing the movable contact assembly to theopen circuit position, and the second serially related are assistingopening mo-v tion of the driving piston during high currentinterruption.

2. A circuit interrupter of the liquid break type including a casing, arod-shaped relatively stationary contact disposed adjacent one end ofthe casing, a movable contact assembly movable within the casingincluding a hollow piston member through which liquid may flow, an intermediate contact and a driving piston, the intermediate contact beingcooperable with the relatively stationary contact to establish an arc.

a movable contact movable adjacent the other end of the casing andcooperable with the intermediate contact to establish a second seriallyrelated arc, the rod-shaped relatively stationary contact protrudingthrough the hollow piston member to engage the intermediate contact inthe closed. circuit position of the interrupter, liquid inlet passagemeans disposed in the movable contact assembly adjacent the point ofengagement of the stationary and intermediate contacts, means biasingthe movable contact assembly to the open circuit position, the secondserially related are assisting opening motion of the driving pistonduring high current interruption, the casing having a widened portionand a restricted portion, and the hollow piston moving from the widenedportion into the restricted portion to thereby provide a time delaybefore application of liquid to the first said arc.

3. A circuit interrupter of the liquid break type including a casinghaving an apertured partition member, a relatively stationary rod-shapedcontact disposed adjacent one end of the casing, the casing on one sideof the apertured partition member having an enlarged portion and arelatively restricted portion, a movable contact assembly movablethrough the aperture in the partition member and including a hollowpiston member through which liquid may flow, an intermediate contact anda driving piston, the rodshaped stationary contact extending through thehollow piston member to engage the intermediate contact in the closedcircuit position of the interrupter, a rod-shaped movable contactmovable through the driving piston to engage the intermediate contact inthe closed circuit position, the relatively stationary contact and theintermediate contact being cooperable to establish an arc within thehollow piston member, the movable contact being cooperable with theintermediate contact to establish a second serially related arc, thehollow piston member moving from the enlarged portion of the casing tothe restricted portion thereof, inlet passage means provided in thecontact assembly adjacent the point of engagement of the stationary andintermediate contacts, the driving piston being disposed on the otherside of the partition member, means biasing the movable contact assemblyto the open circuit position, and the said second arc assisting thedriving piston during high current interruption.

4. A circuit interrupter of the liquid break type including a casing, arod-shaped relatively stationary contact disposed adjacent one end ofthe casing, a movable contact assembly movable within the casingincluding a hollow piston member through which liquid may flow, anintermediate contact and a driving piston, the intermediate contactbeing cooperable with the relatively stationary contact to establish anare which is subjected to the liquid flow passing through the hollowpiston, a movable contact movable adjacent the other end of the casingand cooperable with the intermediate contact to establish a secondserially related arc, the rodshaped relatively stationary contactprotruding through the hollow piston member to engage the intermediatecontact in the closed circuit positionof'the interrupter, liquid" inletpassage'means disposed in the movable "contact assembly ad jacent thepoint'ofengagement of the stationary current-interruption, and theintermediate "contact having a lost-motion mechanical connection withthe movable contact assembly.

5. A circuitinterrupter'of the liquid'breaktype including .-a casinghaving an apertured partitionmember, a relatively stationary rod-shapedcontactadisposed:adjacentone end'of the casing, a movable contactassembly movable through the :aperture in the partition member andincluding a hollow piston member through which liquid may now, anvintermediate contact and adriviing piston,'the rod-shaped stationarycontact extending at least part way through the hollow piston membertoengage the intermediate contact in the closed circuit position of theinterrupter, a trod-shaped mov'abl'e contact movable through the drivingpiston to engage the intermediate contact in the closed circuitposition, the relatively stationary contact and the intermediatecontac't being coopera'ble to establish "an are within the hollow pistonmember which is subjected to the liquid flow passing through :the:hollow piston member, the movable contact being co'operable with theintermediate contact to establish :asecond serially related :arc, inletpassage means provided in the movable contact assembly adjacent thepoint of engagement of the stationary .and intermediate con tacts, thedriving piston being disposed on the other side of the partition member,means bias-- ing the vmovable contact (assembly to the "open circuitposition, the said second are assisting the driving piston during highcurrent interruption, and the intermediate contact having a lost-motionmechanical connection with the movable contact assembly.

6. A circuit interrupter of the liquid break type including a casing, adifferential piston movable within the casing carrying a movable hollowmember of appreciable length therewith through which liquid may flow, arelatively stationary contact extending into the hollow member, a rodshaped movable contact making engagement with the stationary contact inthe closed circuit position, and means biasing the differential pic ton.member to the open circuit position.

'7. A circuit interrupter of the liquid break type including a. casinghaving an apertured partition member, a movable differential pistonassembly movable through the aperture and carrying a movable hollowmember of appreciable length 8 therewith through which liquid'mayflowm'rela'e tively stationary contactga movablecontaict gaging thestationary contact adjacent'the lint'e'rio'r of the hollow memberyandmeans biasing the differential pistonmember totheope'n circuit position.

8. A circuit interrupteref the liquldbreak'type including a casinghaving-an apertured partitioh member, a movable ='difierentia1 :pi'stonassembly movable through "the aperture and carrying "a movable holl'o'wmember of appreciable l'ngth therewith through which liq'ilid may fl6W,"a 1 61 tively stationary contact, a "movable contact engaig'ing thestationary contact the interior of the hollow'meinber, 'mea'nsbiasin'gthe differential pisto'n member to the open circuit position, thedifiereritial pistonmember having two piston surfaces or unequal area,the eas ng having on one Side of the partition member -an enlargedportion and a iistricted portion, and the smaller piston *s'urfacemoving from the "ehlarged portion into the restricted portion.

9. A circuit interrupterof the lidiiid br'eaktype including a casing-arelatively s'tatioha'rfy' coiitblct disposed adjacent one end of thecasing, e mov able contact assembly including a pis'ton, a ableintermediate contact and a driving ipistbnthe movable intermediateeontact sepam g from the relatively stationary contact to' establish anarc, the "first said 'piston'de'iiiiing cashmere orifices through whichsaid are i the opening operation, the "opening motion of the first saidpiston causing now or I liquid through said one or more orinees adjacentsaid arc, a movable contact disposed adjacent the other end of thecasing and cooperable with the intermediate contact to establish asecond serially related arc, means utilizing the pressure from thesecond arc to accelerate motion of the driving piston during highcurrent interruption, and the movable contact having an opening movementin the same direction as opening movement of the intermediate contact.

LEON R. LUDWIG, WINTHROP M. BENJAMIN 1'2. BAKER. J-. CUMMING, Executrixof the estate of James -M. Cumming,

deceased.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,077,338 Lingal et a1 Apr. 13, 193"? 2,235,901 Ronnberg Mar.25, 1941 2,420,889 Leeds May 20, 19 1": 2,456,926 Cumming Dec. 21, 1948

